高強度鋼のΔKが4MPa√m以下の極低速き裂進展挙動について

抄録

High Strength Steel shows internal origin type fatigue failure as called Fish eye failure in low stress and high cycle region. In this failure, ODA is formed on the fracture surface. Although the explication of the mechanism of ODA formation is needed for the explication of the Fish eye failure mechanism, the explication is not yet accomplished. It’s reported that internal fatigue crack in high strength steel is propagating extremely slowly by recent investigations. And crack propagation rate was suggested that series of the low alloy steel depend on the maximum stress and ΔK. In this study, fatigue test of the same material was in vacuum environment. As a result, ΔK≤4 MPa√m as for crack propagation rate, it suggested that the test on condition of long initial crack was faster than the test on condition of short initial crack. Therefore crack progress speed depend on the test conditions as well as the maximum stress.